Thermoplastic compositions containing aromatic polycarbonate, polyalkylene terephthalate and an elastomeric impact modifier are known and available commercially. The impact modifiers thus suitable include acrylonitrile-butadiene-styrene copolymer (ABS) or methyl methacrylate-butadiene-styrene copolymer (MBS).
The published art is noted to include U.S. Pat. Nos. 5,104,934 and 5,082,897 that disclosed thermoplastic molding compositions containing polycarbonate, polyesters and ABS or ASA (acrylate-styrene-acrylonitrile). These compositions are said to exhibit enhanced moldability, heat resistance and thick section impact resistance. Also relevant is U.S. Pat. No. 4,554,315 that disclosed a thermoplastic molding composition containing polyester resin, polycarbonate resin, and a graft polymer based on conjugated diene or acrylate rubber and includes a grafted phase that may include methacrylic ester and styrene.
U.S. Pat. No. 4,877,835 disclosed a thermoplastic resin composition containing a rubber-modified styrene thermoplastic resin, an aromatic polyester, and aromatic polycarbonate. Included among the rubber modified styrene thermoplastic resin is methylmethacrylate-butadiene-styrene resin.
U.S. Pat. No. 4,888,388 disclosed an impact resistant thermoplastic composition having distinguished surface appearance, color and thermal stability. The composition contains a graft rubber copolymer, polycarbonate and saturated polyester.
U.S. Pat. No. 5,674,928 disclosed a thermoplastic resin composition containing a polyester resin, a polycarbonate resin and a graft copolymer containing a rubbery substrate and a rigid superstrate. Methylmethacrylate-butadiene-styrene graft copolymers are among the disclosed graft copolymer.
JP 2001 031 860 disclosed a composition containing polycarbonate, a mixture of polyethylene terephthalate and polybutylene terephthalate and a graft elastomer having a core-shell structure. The composition said to exhibit high impact strength, hydrolytic stability and chemical resistance.
An impact modified thermoplastic molding composition containing polycarbonate, polyalkylene terephthalate and a graft (co)polymer has been disclosed in U.S. Pat. No. 7,067,567. The graft (co)polymer is exemplified by methyl methacrylate-grafted silicone-butyl acrylate composite rubber. U.S. Pat. No. 6,989,190 disclosed a blend of polycarbonate, cycloaliphatic polyester resin and an impact modifier that contains a MBS core-shell polymer.
Among the objectives of the present invention was the development of a thermoplastic composition that features good mechanical properties and surface appearance.